Extensive characterization of pristine nanomaterials (NMs), also called nanoparticles (NPs), is of importance to understand and control their interactions with biological systems. Indeed it becomes more and more apparent that NMs, besides their advantages in a large number of areas, potentially present negative effects on living organisms.
Indeed the NM surface hydrophobicity has e.g. been reported to have a critical role in the cellular uptake, toxicity, and immune responses to nanomaterials. NMs with a high degree of surface hydrophobicity were also shown to demonstrate severe hemolysis. According to some sources, NMs with decreasing surface hydrophobicities have an influence on plasma protein adsorption. Furthermore, in the development of nanoparticle-based vaccine adjuvants, the hydrophobicity of NMs was said to be a key factor for changing the interaction with immune cells.
Although these are only a few examples, it seems that main properties for which determination of reliable and reproducible data would be desirable are:
(1) NMs size and size distribution,
(2) Surface properties (surface charge, hydrophobicity), and
(3) Optical, mechanical, magnetic properties.
In particular, surface charge and hydrophobicity properties have shown to have direct effects on NMs functionality and toxicity.
Multiple characterization techniques allowing the characterization of NM properties exist, but there is currently no single method enabling the determination of the surface properties and the size distribution in one step.
NMs size and size distribution can be determined by using a combination of optical/imaging techniques, whereas surface properties can be determined with surface analysis techniques (XPS [X-ray photoelectron spectroscopy], ToF-SIMS [Time of Flight Secondary Ion Mass Spectrometry]). These methods are very sensitive, but unfortunately are time consuming and require expensive equipment and specialized expertise.
The constant increase of the NMs present in consumer products in a huge number of fields and the high number of new nanomedicines based on NMs make urgent the need to develop new tools enabling rapid characterization of NMs properties such as particular size, surface chemistry and hydrophobicity.